Russia's parliament has given its initial backing to a visa bill that could lead to a ban on foreign visitors showing "disrespect" to the country.

Anyone found by a court to have offended Russian values, authorities or symbols may be barred from entering but the bill does not define such offenses.

The bill would also restrict entry for people with infectious disease conditions such as HIV.

Rights groups fear it could be used to keep government critics out of Russia.

The bill must pass another two readings in the Duma before it can be ratified.

The Duma, or lower house of parliament, passed the bill in its first reading without debate.

The BBC's Steve Rosenberg reports from Moscow that it is a bill designed to enhance Russia's national security, but it raises the fear of new barriers between East and West.

'Nothing complicated'

In the words of the bill, which contains nearly 100 amendments to laws governing the status of non-Russians, foreign nationals can be kept out for having harmed Russia's "generally accepted spiritual, cultural and social values".

The bill does not specify what these values are.

Symbols of Russia, ranging from flags to images of its leaders, are known to have been mocked or defaced in former Soviet republics.

Anyone judged by a court to have damaged the country's reputation abroad could be affected, with the decision in each case taken by either the president, parliament, government or a court, said one of the bill's authors, Vladimir Pligin.

"The restriction will be imposed only when the fact of committing disrespectful actions is established in court," he said.

A spokesman for Human Rights Watch in Moscow told the BBC that, if adopted, the law would give the government a free hand to close the borders to anyone who was not welcome in Russia.

Curbs are proposed on foreign visitors who are addicted to drugs or have infectious diseases.
Under the law, long-term visas could be denied to anyone who cannot prove they are not carrying the HIV virus, which causes Aids.

Mr Pligin told Reuters news agency there was "nothing complicated" about the bill.